SYSTEM INCLUDING SENSING ELEMENTS AT DIFFERENT DISTANCES FROM VERTICAL MAGNETIC FIELD LINES

• US 20090146647A1
• Filed: 12/05/2007
• Published: 06/11/2009
• Est. Priority Date: 12/05/2007
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Ausserlechner, Udo
• Granted Patent: US 8,575,920 B2
• Time in Patent Office: Days
• US Class Current: 324/207.210
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence
• CPC Class Codes: G01P 3/488 delivered by variable reluctance detectors

Abstract

A system including a magnet, a first magneto-resistive sensing element, and a second magneto-resistive sensing element. The magnet is configured to provide a magnetic field. The first magneto-resistive sensing element is situated in the magnetic field and the second magneto-resistive sensing element is situated in the magnetic field. The second magneto-resistive sensing element is laterally a greater distance from vertical magnetic field lines of the magnetic field than the first magneto-resistive sensing element.

Claims

1. A system comprising:

a magnet configured to provide a magnetic field;

a first magneto-resistive sensing element situated in the magnetic field; and

a second magneto-resistive sensing element situated in the magnetic field, wherein the second magneto-resistive sensing element is laterally a greater distance from vertical magnetic field lines of the magnetic field than the first magneto-resistive sensing element.

2. The system of claim 1, wherein the vertical magnetic field lines intersect the first magneto-resistive sensing element.

3. The system of claim 1, wherein the magnitude of the x-component of the magnetic field through the second magneto-resistive sensing element divided by the magnitude of the x-component of the magnetic field through the first magneto-resistive sensing element is greater than 2.

4. The system of claim 1, wherein the vertical magnetic field lines are laterally offset from a centerline between the first magneto-resistive sensing element and the second magneto-resistive sensing element by greater than ⅛

^th of the spacing between the first magneto-resistive sensing element and the second magneto-resistive sensing element.

5. A system comprising:

a magnet configured to provide a magnetic field;

a first magneto-resistive sensing element situated in the magnetic field; and

a second magneto-resistive sensing element situated in the magnetic field, wherein the first magneto-resistive sensing element and the second magneto-resistive sensing element are configured to be differently saturated, such that the second magneto-resistive sensing element is closer to saturation than the first magneto-resistive sensing element.

6. The system of claim 5, wherein the first magneto-resistive sensing element is situated in vertical field lines of the magnetic field and the second magneto-resistive sensing element is situated in diverging field lines of the magnetic field.

7. The system of claim 5, wherein the magnitude of the x-component of the magnetic field through the second magneto-resistive sensing element divided by the magnitude of the x-component of the magnetic field through the first magneto-resistive sensing element is greater than 2.

8. The system of claim 5, wherein the magnetic field has a vertical symmetry plane that is laterally offset from a centerline between the first magneto-resistive sensing element and the second magneto-resistive sensing element by greater than ⅛

^th of the spacing between the first magneto-resistive sensing element and the second magneto-resistive sensing element.

9. The system of claim 5, comprising a third magneto resistive sensing element situated between the first magneto-resistive sensing element and the second magneto-resistive sensing element.

10. The system of claim 9, wherein the magnetic field provides vertical field lines between the first magneto-resistive sensing element and the third magneto-resistive sensing element.

11. The system of claim 5, comprising a toothed magnetically permeable wheel configured to rotate in the magnetic field and provide a modulated magnetic field, wherein the first magneto-resistive sensing element responds to the modulated magnetic field.

12. The system of claim 5, wherein the first magneto-resistive sensing element and the second magneto-resistive sensing element are part of a sensor bridge.

13. The system of claim 12, comprising:

a third magneto-resistive sensing element situated in the magnetic field and coupled in series to the second magneto-resistive sensing element; and

a fourth magneto-resistive sensing element situated in the magnetic field and coupled in series to the first magneto-resistive sensing element, wherein the third magneto-resistive sensing element is unsaturated and the fourth magneto-resistive sensing element is saturated via the magnetic field.

14. A system comprising:

a magnet; and

a sensor bridge including;

first magneto-resistive sensing elements and second magneto-resistive sensing elements adjacent the magnet;

third magneto-resistive sensing elements and fourth magneto-resistive sensing elements laterally offset from vertical magnetic field lines of the magnet a greater distance than the first magneto-resistive sensing elements and the second magneto-resistive sensing elements; and

at least one switch configured to select which of the first, the second, the third, and the fourth magneto-resistive sensing elements are in a first resistor divide network and a second resistor divide network to substantially eliminate an offset voltage.

15. The system of claim 14, wherein the first and the second magneto-resistive sensing elements are unsaturated and the third and the fourth magneto-resistive sensing elements are saturated via the magnet.

16. The system of claim 14, comprising a toothed magnetically permeable wheel configured to rotate in the magnetic field and provide a modulated magnetic field, wherein the sensor bridge senses the modulated magnetic field.

17. The system of claim 14, comprising a fifth magneto resistive sensing element situated between the first magneto-resistive sensing elements and the third magneto-resistive sensing elements.

18. The system of claim 17, wherein the magnet is situated to provide the vertical magnetic field lines between the first magneto-resistive sensing elements and the fifth magneto-resistive sensing element.

19. A method of sensing comprising:

providing a magnetic field;

providing an unsaturated magneto-resistive sensing element via the magnetic field;

providing a magneto-resistive sensing element that is closer to saturation than the unsaturated magneto-resistive sensing element via the magnetic field; and

responding to changes in the magnetic field via the unsaturated magneto-resistive sensing element.

20. The method of claim 19, wherein responding to changes comprises:

sensing changes in the magnetic field via the unsaturated magneto-resistive sensing element; and

maintaining the magneto-resistive sensing element that is closer to saturation in saturation.

21. The method of claim 19, comprising:

rotating a magnetically permeable wheel in the magnetic field to provide a modulated magnetic field, wherein responding to changes comprises;

sensing the modulated magnetic field via the unsaturated magneto-resistive sensing element.

22. The method of claim 19, comprising:

providing a direction sensing magneto-resistive sensing element in the magnetic field; and

sensing the rotational direction of the magnetically permeable wheel via the direction sensing magneto-resistive sensing element.

23. A method of sensing comprising:

providing a magnetic field via a permanent magnet; and

sensing via a sensor bridge in the magnetic field, wherein sensing comprises;

providing vertical magnetic field lines to first magneto-resistive sensing elements and second magneto-resistive sensing elements;

providing diverging magnetic field lines to third magneto-resistive sensing elements and fourth magneto-resistive sensing elements; and

selecting which of the first, the second, the third, and the fourth magneto-resistive sensing elements are in a first resistor divide network and a second resistor divide network to substantially eliminate an offset voltage.

24. The method of claim 23, wherein

providing diverging magnetic field lines to third magneto-resistive sensing elements and fourth magneto-resistive sensing elements comprises:

saturating the third magneto-resistive sensing elements and the fourth magneto-resistive sensing elements.

25. The method of claim 23, comprising:

rotating a toothed magnetically permeable wheel to provide a modulated magnetic field;

sensing the modulated magnetic field via the first magneto-resistive sensing elements and the second magneto-resistive sensing elements; and

maintaining the third magneto-resistive sensing elements and the fourth magneto-resistive sensing elements in saturation.